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Developing your scientific skepticism: The Tu Quoque Fallacy

To become a more effective scientific skeptic, you need to know your logical fallacies. This is part two of my irregular series – my first was on the middle ground fallacy. Today’s focus is a very, very common fallacy: Tu quoque.

The tu quoque argument ( Latin for “you, also”) is a type of ad hominem argument – literally, “to the person”. It is a statement about the person, and not about the the statement being made. In my posts about homeopathy, this fallacy is frequently used by commenters. For example, I recently posted about an uncritical endorsement of homeopathy by a medical doctor. Notably, that physician acknowledges that homeopathy has no medicinal ingredients – it is a placebo. Not surprisingly the responses from homeopathy advocates ignores the consensus that homeopathy has no medicinal effects. Instead the comments tend to cite problems with real medicine. Commenter Avijit first quotes from a commentary in JAMA that claims:

225,000 people have died in one year in the US alone due to iatrogenic diseases. Of these 140,000 has been exclusively due to adverse drug reactions. In addition, an equal number died during out patient management of Adverse Drug Reactions that cost the buyer a total of $ 79 billion in prescription bills in one year.

Uncertainty creeps into medical practice through every pore. Whether a physician is defining a disease, making a diagnosis, selecting a procedure, observing outcomes, assessing probabilities, assigning preferences, or putting it all together, he is walking on very slippery terrain. It is difficult for non physicians, and for many physicians, to appreciate how complex these tasks are, how poorly we understand them, and how easy it is for honest people to come to different conclusions.

Mainstream medicine is based upon a culture and institution of science, and a science-based standard of care. The execution of this standard is flawed, but the principle is clear. CAM is not based on a science-based standard. It, in fact, seeks to subvert and even remove the science-based standard of care. And CAM proponents live in a culture of pseudoscience, not legitimate science. To the extent that the science-base of modern medicine is not adequate the proper response is to improve the science (a never ending task), not to use methods that are even less science-based. CAM is largely devoid of science. CAM proponents, to borrow an excellent turn of phrase, use science as a drunk uses a lamppost – for support rather than illumination.

When you see the tu quoque fallacy used, it’s a sign of desperation – unable to respond to the question at hand, the user has decided to attack something else. Even the author of the original post, Dr. Des Spence, used a tu quoque, to defend his argument:

The saga of COX-2 drugs and the unethical, illegal behavior of Merck are real issues in medicine, but are irrelevant to the topic that was under discussion: The ethics of deceiving patients by giving them sugar pills. Vioxx does not make homeopathy ethical! The solution to ineffective regulation and criminal behavior is to fix the problem and do it better – not to decide to abandon science for magical thinking about vitalism. Science standards are equally applicable to all health interventions. And a single scientific standard should be applied to everything – we should not accept a lowered bar for safety and effectiveness just because something is “Eastern”, “Alternative”, “Holistic”, “Individualized”, “Integrative” or whatever buzzword you wish to attach to your preferred form of pseudoscience.

Brace Yourself
Physician and author Ben Goldacre has a new book out, a follow-up to the excellent Bad Science. This one is called Bad Pharma, and judging by the excerpts, promises to be a detailed analysis of the behaviour of pharmaceutical companies. I’m interested to see what he recommends to improve the practice of medicine. While I haven’t read the book yet, I doubt Goldacre concludes it with, “Therefore homeopathy works.” But that doesn’t mean you won’t see this argument from others. Science advocates should be prepared for a lot more tu quoque statements.

……….not to decide to abandon science for magical thinking about vitalism.

This is what a homeopathic doctor wrote during the Spanish flu in the USA:

“Aspirin and the other coal tar products are condemned as causing great number of unnecessary deaths. The omnipresent Aspirin is the most pernicious drug of all. It beguiles by its quick action of relief of pain, a relief which is but meretricious. In several cases Aspirin weakened the heart, depressed the vital forces (?), increased the mortality in mild cases and made convalesce slower.”

Do you understand what he means here by vital force or it requires explanation?

So now vital force is “unnecessary” and represents “magical thinking.” Look, a mini Rubricon skeptics will have to cross in order to reach the realm known as “persuasive and trustworthy” is that boundary where they suddenly realize they should take special care in labeling things which they dont completely understand. Yes, the points about homeopathy defenders trying to divert attention rather than defend are valid. But vitalism cannot be disproven. There are many phenoms you can prove exist but you can’t prove dont exist. This is because we use means to empirically measure things; some things claimed to exist may be impossible to debunk because of the extant possibility the proper means to measure a manifestation of the concept has yet to be invented. Just because chemistry places limits to the principles of water with terms like hydrogen bonding and van der walls forces doesn’t mean there is not another force or and interaction of existing forces at play to create vitalistic effects. Furthermore, researchers need some objectivity and incentive to even look to develop tools that could measure such a force. True CAM and others are sloppy with language and they hasty generalize. But skeptics have these probs as well.